Jack assemblies

ABSTRACT

A jack assembly has a blocking mechanism to prevent the loaded gripper from being opened before the load has been raised a certain distance by another gripper, thus ensuring that the load has actually been taken over by said gripper.

United States Patent Ahlgren et al.

1 51 3,685,801 1451 Aug. 22, 1972 1541 JACK ASSEMBLIES [72] Inventors: Nils Harald Ahlgren, Skyttevagen 22 8-133, Saltsjobaden, Sweden;

Odd Jahr, Fjordveien 50, Oslo, Norway 1 [22] Filed: 7 Dec. 22, 1969 [21] Appl. No.: 886,903

52 vs. C] ..254/105 51 Int. c1.....-...; ..B66f 1/00, E02d 21/00 [58] Field Of Search ..254/105-107 [56] References Cited UNITED STATES PATENTS 3,203,669 8/1965 Johansson 154/107 3,207,475 9/1965 Johansson ..-..254/105 3,347,522 10/1967 Reinmann ..254/1( )5 FOREIGN PATENTS OR APPLICATIONS 43,557 12/ 1965 Germany ..254/l06 110,712 3/1961 Pakistan ..254/l06 Primary Examiner-Othell M. Simpson I I Attorney-Ralph E. Bucknam, Jesse D1 Reingold Robert R. Strack and Henry A. Marz'ullo,-Jr.

[ ABSTRACT A jack assembly has a blocking mechanism to prevent the loaded gripper from being opened before the load has been raised a certain distance by another gripper, thus ensuring that the load has actually been taken over by said gripper.

7 Claims, 14 Drawing Figures FATE-INTER M1222 m2 FIG.3C FIG. 3d

PATENTEBMIBZZ m V I 3; 685. 801

SHEET 3 BF 4 FlG.5

JACK ASSEMBLIES Swedish Pat. No. 149,327 discloses a jack assembly which permits moving the load both in the direction of the lines of force of the load and in the opposite direction with the aid of a movable gripper connected to the piston and a gripper fixedly connected to the piston housing. n raising of the load the unloaded gripper is kept pressed against the lifting rod profile under spring force and is brought into engagement with said profile by wedge action when the force is transferred from the earlier loaded gripper. On lowering of the load, however, the nonloaded gripper must be opened to let the lifting rod pass and be closed when it shall take over the load. The movement of the piston controls the opening and closing movements of the gripper, but there is the risk that the loaded gripper may be opened before the earlier unloaded gripper has taken over the load. The present invention has for its object to eliminate this risk by the provision of a blocking mechanism which prevents the opening means from opening the loaded gripper before the load has been raised a certain distance by another gripper, thus making sure that the load has actually been taken over by said gripper. I

When the load has been raised and the blocking mechanism has released the opening means to cause them to open the now unloaded gripper, said gripper can be returned by the piston to the initial position for lowering of the load. During this movement the opening means keep the gripper open, while the blocking mechanism prevents the gripper from closing. When the initial position for lowering of the load has been reached the blocking mechanism releases the opening means whereby the gripper is closed. This gripper now takes over the load and can start lowering it.

By having two jacks of the above function alternate in taking over the load from one another one attains a quicker raising or lowering than is realized by previously known jacks, since the return movement of the unloaded gripper can be effected simultaneously as the loaded gripper moves the load.

On lowering of the load the pressure medium is passed from the piston housing of the loaded gripper to that of the unloaded gripper, which results in a quicker return movement than that obtained with an economically dimensioned pumping device.

If the discharged pressure medium in a first phase is caused to urge, through a pressure changing device, a greater amount of pressure medium into the piston housing the piston of which is to be returned, and the pressure changing device is switched over in the final phase, the earlier unloaded gripper will take over so large a proportion of the load that the opening means can open the gripper which hands over the load.

The simultaneous use of several such pairs of alternately operating jacks for moving a rigid load is advantageous insofar as the load will always be supported by an oil bed common to all jacks, implying an equal distribution of the load on all of the jacks. In previously known jacks in which a fixed gripper alternately takes over the load there cannot take place any load equilibration. If a further load equilibration is required the pair of jacks is equipped with a piston device the pressure medium of which is discharged through an adjustable overflow valve if the load exceeds the contemplated load on the jack.

At the simultaneous use of several jacks equipped with such overload protecting means the jacks can be connected to the sarneoverflow valve, provided the injection of pressure medium'into the jacks is prevented by check valves which will ensure that the other jacks are not affected by one jack being under an overload. The above mentioned check valves can be dispensed with by repeated supply of pressure medium to the overload protecting means so that these are always in application against upper abutments.

It is to be understood by the artisan that while the invention as hereinafter described refers to the load support element as a rod, any other equivalent support element can be used in connection with the jack assembly of this invention, such as for example an elongated cable.

The accompanying drawings illustrate an embodiment of the invention, but the invention can of course be embodied in other ways within the scope of the appended claims.

In the drawings:

FIG. 1 shows a longitudinal section of a jack assembly;

FIGS. 2a and b shows two operating stages in raising a load with the aid of two alternately operating jacks;

FIGS. 30, b, c and d shows various operating stages in lowering a load with the aid of two alternately operating jacks;

' FIG. 4 shows the connection of two alternately operating jacks via a pressure changing device;

FIG. 5 shows jacks equipped with overload protecting means;

FIG. 6 shows a jack having a spring-loaded friction device for stretching and centering the lifting rod;

. FIG. 7 shows how the gripper is made to open for lateral insertion of the lifting rod;,

FIG. 8 shows how two alternately operating jacks are connected to their pressure medium sources;

FIG. 9 shows two alternately operating pairs of jacks arranged side by side on a common baseplate;

FIG. 10 shows a top plan view of the arrangement illustrated in FIG. 9.

As long as the stop bolts 1 are inserted in holes through the outer housing 2 of the jack and through the slides 3 of the blocking mechanism, the slides are prevented from being unseated from the adjustable abutment 4.'When the piston 5 is raised by supplied pressure medium it moves the ball holder 7 and the gripper 8 upwards by means of the rods 6, compresses the return spring 9 and ejects the oil from the return piston 35.

The balls 10 of the blocking mechanism are kept in unaltered position by the slides 3 so that the knock-out sleeve 11 of .the opening means cannot be thrown by the knock-out spring 13 against the wedges 12 of the pp The wedge springs 14 keep the wedges 12 permanently urged against the lifting rod 15, and the wedges catch hold when the gripper is moved upwards, but slide without any engagement along the lifting rod when the return spring 9 and the return piston 35 move the gripper downwards. The jack now functions as a lifting jack and can operate alternately withanother jack of this type or a gripper fixedly mounted in relation to the jack housing.

' reached the lower extreme position and takes over the load as soon as the oil pressure in the upper jack is allowed to sink.

The stop bolts 1 are removed when the load is to be lowered. The jack shown in FIG. 1 has effected a lowering phase and its gripper shall be opened to permit beingreturned to initial position forthe next lowering phase. The friction device 16 has been set for the desired friction by tightening of the set screw 17. As a result the spring 18 is compressed so that the friction device 16 is displaced sufl'iciently to allow the stop pin fixedly connected to the jack housing 2.

When the lifting rod 15 is moved in relation to the jack in a direction opposite to that of the lines of force of the load as proof of the fact that another gripper has taken over the load, the friction device partakes in the movement of the lifting rod and raises the slides 3 which move with regard to the bolts 22 by reason of elongated holes in the slides 3.It will be noted that the friction device 16, 17, 18 is disposed in an opening of the slides 3. The friction deviceengages the lifting rod 15 with a friction engagement whereby the slides 3 will be moved with the movement of thelifting rod 15 when the latter is lowered. As indicated above, the frictional force between the friction device and lifting rod is set by means of the set screw 17 and thus the frictional force is not changed with each lifting or lowering step.

' The balls 10 of the blocking mechanism can now be urged out of their recesses in the slides so that the knock-out sleeve 11 is thrown by the knock-out spring 13 against the wedges 12, thereby opening the gripper. When the opened gripper is by the piston 5 and has caught up with the slidesfthe balls are again urged into the ball holder 7 by the bevelled surface of the slides.

The balls 10 are now located beneath the bead of the knock-out sleeve. 11 thus preventing the latter from being returned by the distance spring 23 and the wedge 19to pass through thehole 20in the plate 21 which is jacks are simultaneously brought into newengagement,

which is realized by a stop device 37-arresting the .return movement of the gripper 8 until the pressure of the pressure medium has risen to a value dependent on the setting of the stop device. This will eliminate differences in the jack movements caused by varying frictional forces. On lowering of theload the now loaded gripper moves downwards and the balls l0 will be urged by the upper bevelled surface of the slides 3 into ball holder 7 above the bead of the knock-out sleeve In the final phase of the lowering movement. the

knock-out sleeve 11 compresses the knock-out spring 13 and has thereby returned into initial positioin How two alternately operating jacks coact will appear from FIG. 3. In FIG. 3a the upper. jack has lowered the load to the desired position and the gripper. of the lower jack has been closed at the upper extreme position. By supply of further pressure medium to the lower jack in FIG. 3b this jack will'take over the load and.

raise it a sufficient distance to cause the friction device to raise the slides and release theballs so that the knock-out sleeve can strike back the wedges. As will appear from FIG. 3c the lower jack can now lower the load while the opened gripper of the upper jack is whereby the piston and the opened gripper of the latter jack are raised into initial position for lowering of the load. Setting of the valve system 26 into the intermediate position will connect a pressure changing device 27 which in the first phase. supplies a greater quantity of pressure medium to the piston housing '25 springs 14 when the knock-out spring 13 does not the knock-out sleevell any more. When the gripper of the other jack starts lowering the lifiing rod 15 the friction device 16 pulls the slides 3 downwards into initial position. When the load lowering jack has reached its desired final position the opened gripper is moved towards the upper extreme position, the knock-in spring 36 being compressedby the wedges 12, and when the balls 10 arrive at the upper bevelled surface of the slides 3 they can be urged out of the ball holder 7 by the bead of the knock-out sleeve 11 under the pressure of the distance spring 23,

Should thepiston devices 2810f several jacksabe .con-

nected to the same overflow valve 29 check valves 30 than what is discharged from the piston housing 24. In the final phase the valve system is shifted a further step so that the pressure changing device 27 is connected in the reverse order into the system. As a result, the earlier unloaded gripper inthe lower jack can take over the 'rnajor proportion of the load from thegn'pper of the upper jack so that the latter gripper can be opened.

FIG. 5. shows how a pair of jacks is equipped with overload protecting means in "the form of a piston device 28 which is connected toan overflow valve 29.

are required in the conduits in order that pressure medium discharged from a piston device 28 shall not be driven into any other piston device 28. Alternatively,

the check valves 30 can be dispensed with if it is'made sure that the pistons of the piston devices are permanently kept in application withupper abutments by means of connections 31 that lead tothe pressure medium system of the jacks and are equipped with check valves.

FIG. 6 shows a pair of jacks in which a friction device 32 with the aid of a spring mechanism keeps the lifting I Y rod 15 in correct position and stretched so that the gripper of the upper jack will have the same favorable operating conditions as the gripper of the lower jack.

FIG. 7 shows how the gripper is designed so as to permit opening thereof for lateral insertion of the lifting rod 15 thereinto. The gripper whose wedges 12 retain the lifting rod 15 from all sides, is kept together in closed position by a bolt assembly 33, a joint 34 or a hydraulic clamping device of a suitable, previously known type.

FIG. 8 shows that the supply line 38 for supplying pressure medium to the lifting piston in the lower jack 39 has a branch conduit 40 leading pressure medium to the return piston in the upper jack41. In the same way the supply line 42 for supplying pressure medium to the lifting piston in the upper jack 41 has a branch conduit 43 leading pressure medium to the return piston in the lower jack 39.

In FIG. 9 it is shown how a pair of jacks 45 which by means of the rods 46 are connected to an upper gripper 47 can be mounted on a baseplate 44 laterally of another pair of jacks 49 which by means of the rods 50 are connected to a lower gripper 51. The pairs of jacks operate alternately in displacing the rod element 48, a common friction device 53 actuating blocking means 54 and 55 for lower grippers 51 and upper grippers 47, respectively.

In FIG. it is shown how each jack pair 45 and 49, respectively, is placed in such a manner that the rod element 48 will lie in the resultant line of the piston forces. What we claim and desire to secure by Letters Patent 1. In a jack assembly having grippers moveable relative to a housing and which forcibly engage a loaded elongated support element to controllably move same longitudinally, the improvement which comprises grippers which when engaged with the support element constrain same against longitudinal movement relative to the grippers in the load direction and allow relative movement ofthe support element in the opposite direction; opening means operable to disengage said grippers from the support element, said opening means including means operable to move said support element opposite the load direction by a predetermined amount upon occurrence of a predetermined condition; and blocking means operable in response to movement of the support element opposite to the load direction to activate said opening means and thereby disengage the grippers from the support element upon occurrence of said predetermined amount of support element movement opposite the load direction.

2. In a jack assembly having grippers moveable relative to a housing and which forcibly engage a loaded elongated support element to controllably move same longitudinally, the improvement which comprises grippers which when engaged with the support element constrain same against longitudinal movement relative to the grippers in the load direction and allow relative movement of the support element in the opposite direction; opening means including a releaser element moveable relative to said grippers from a retracted position, at which the grippers are free to engage the support element, to a forward position of engagement with the grippers to thereby disengage the grippers from the support element; and blocking means operable to selectively retain said releaser element in one of said forward and retracted positions, whereby when said blocking means is operated to retain the releaser element in e retracted posltion, the grippers are free to engage the support element, and when the blocking means is operated to retain the releaser element in the forward position, the grippers are disengaged thereby from the support element.

3. The improvement according to claim 1 including friction means connecting said blocking means to said support element for response to the movement thereof.

4. The improvement according to claim 1 wherein said opening means includes a releaser element biased for movement toward the grippers to engage same and thereby disengage the grippers from the support element upon activation of the opening means by said blocking means.

5. The improvement according to claim 1 including friction means disposed in cooperating engagement with said support element to tighten and center said support element in relation to the housing of the jack assembly.

6. The improvement according to claim 1 including fluid pressure powered piston-and-cylinder means coupled to said grippers to urge same into forcibleengagement with said support element.

7. The improvement according to claim 2 wherein said blocking means includes at least one ball disposed forengagement with said releaser element to retain same in its retracted position, and a slide-able member moveable into a position allowing movement of said ball out of engagement with the releaser element to allow said releaser element to move to said forward position to disengage the grippers from the support element. 

1. In a jack assembly having grippers moveable relative to a housing and which forcibly engage a loaded elongated support element to controllably move same longitudinally, the improvement which comprises grippers which when engaged with the support element constrain same against longitudinal movement relative to the grippers in the load dIrection and allow relative movement of the support element in the opposite direction; opening means operable to disengage said grippers from the support element, said opening means including means operable to move said support element opposite the load direction by a predetermined amount upon occurrence of a predetermined condition; and blocking means operable in response to movement of the support element opposite to the load direction to activate said opening means and thereby disengage the grippers from the support element upon occurrence of said predetermined amount of support element movement opposite the load direction.
 2. In a jack assembly having grippers moveable relative to a housing and which forcibly engage a loaded elongated support element to controllably move same longitudinally, the improvement which comprises grippers which when engaged with the support element constrain same against longitudinal movement relative to the grippers in the load direction and allow relative movement of the support element in the opposite direction; opening means including a releaser element moveable relative to said grippers from a retracted position, at which the grippers are free to engage the support element, to a forward position of engagement with the grippers to thereby disengage the grippers from the support element; and blocking means operable to selectively retain said releaser element in one of said forward and retracted positions, whereby when said blocking means is operated to retain the releaser element in the retracted position, the grippers are free to engage the support element, and when the blocking means is operated to retain the releaser element in the forward position, the grippers are disengaged thereby from the support element.
 3. The improvement according to claim 1 including friction means connecting said blocking means to said support element for response to the movement thereof.
 4. The improvement according to claim 1 wherein said opening means includes a releaser element biased for movement toward the grippers to engage same and thereby disengage the grippers from the support element upon activation of the opening means by said blocking means.
 5. The improvement according to claim 1 including friction means disposed in cooperating engagement with said support element to tighten and center said support element in relation to the housing of the jack assembly.
 6. The improvement according to claim 1 including fluid pressure powered piston-and-cylinder means coupled to said grippers to urge same into forcible engagement with said support element.
 7. The improvement according to claim 2 wherein said blocking means includes at least one ball disposed for engagement with said releaser element to retain same in its retracted position, and a slideable member moveable into a position allowing movement of said ball out of engagement with the releaser element to allow said releaser element to move to said forward position to disengage the grippers from the support element. 